For successful autonomous flight, a flight platform must be capable of maintaining stability while carrying out a flight plan. This means all flight tasks such as: takeoff, hovering, flight in a defined route and landing. Flight physical parameters such as: position, velocity, acceleration or more specifically: altitude, vertical (z axis) climb or descent velocity or acceleration, horizontal (x, y axis) position, velocity or acceleration. This capability is particularly difficult to attain for relatively unstable flight platforms, such as small-scale model helicopters or other VTOL (vertical takeoff and landing) vehicles.
In addition to the inherent instability of the platform, it is difficult to calculate the correct output value levels to the servos/actuators that steer the platform in order to control and achieve the required flight parameters. This difficulty is caused by the fact that:                non-stable platforms, especially small-scale platforms, are very sensitive to any changes in their stabilization condition—even a small change for a very short period in the output, or in an environmental factor such as wind speed, can cause an immediate non-stable condition,        input from the sensors regarding the platform flight conditions that are used to calculate the outputs, and the output signal itself, are not always accurate enough or might have insufficient response time or update time (frequency), especially with low end (small size, low weight and cost) sensors,        the output range or the servo or the actuator resolution and accuracy might be relatively narrow, especially in small scale platforms, which are very sensitive to even very small changes in output, and        there is a lag (delay between output and actual platform response), the amount of lag being subject to the flight parameters and the nature of the platform.        
The present invention provides a system (and method) for stable autonomous (or semi-autonomous) flight of non-stable flight platforms. Most fixed wing platforms are designed to maintain stability during flight and will keep their flight condition in all six axes with minimum pilot correction. Non-stable platforms, such as rotating wing, cannot keep their flight condition and without active piloting they will roll over immediately, especially during hovering. This problem is exacerbated in small-scale non-stable platforms.
While the present invention is particularly advantageous for non-stable flight platforms, it can also be applied to improve the flight of inherently stable flight platforms.
The invention introduces the following innovations                Stabilization system and flight control system are separate and operate cooperatively with one another.        Stabilization system can have a dynamic parameter set that adjusts the stabilization parameters in accordance with weather conditions or platform weight changes, thereby improving the platform flexibility (amplitude) and the time required to recover platform stability time.        Instead of a single incremental control output signal, the system provides each cycle a group of outputs. The cycle length and magnitude of output to servos/actuators is modulated.        If a condition of extreme nonstability occurs, the flight control system is disengaged from the platform until the stabilization system regains acceptable stability.        In a case of temporary or major failure in the flight control system, the stabilization system will maintain the platform balanced until recovery and/or will perform an emergency autorotation landing.        A user has the option to temporarily override the flight control system with manual flight commands, or to select semi-auto mode for continuous operation with manual flight commands.        
These innovations are now described in more detail.
The present invention comprises an underlying adjustable stabilization system that provides basic platform aerodynamic stabilization. The invention further comprises a flight control system on top of the stabilization system for controlling various flight parameters and navigation. This system (and corresponding method) overcomes the problem of controlling flight of nonstable platforms (and enhances flight of stable platforms).
The invention further provides dynamic stabilization parameter modification in order to adapt the platform stabilization behavior, flexibility, and recovery time dynamically in accordance with changes in external conditions such as wind magnitude and direction or platform weight changes. These external parameters are monitored, evaluated, and if necessary modified to maintain the required flexibility and recovery time of the platform.
The invention further provides a unique cyclic output method for controlling the required flight parameters via the platform's servos/actuators, which control the platform flight parameters (in the case of rotating wing platforms, this control is expressed in the blade pitch, the rotating plain angle, and the tail rotor pitch). The cyclic output method involves modulating the cycle length and magnitude of the outputs to the servos/actuators such that, instead of a single incremental output calculated by the control algorithm, the output comprises a group (a cycle) of one or more outputs with of greater magnitude than the calculated output and followed by one or more outputs of lesser magnitude than the calculated output, the lesser magnitude are a function of the greater outputs. This overcomes the problems of output signal accuracy and lag response time required for proper control of various flight parameters. This unique innovative method can be implemented, using various basic control algorithms such as PID (proportional, integral and differential) control or fuzzy logic control algorithm, as an intermediate layer between the calculated outputs of the basic control algorithm and the actual outputs to the servos/actuators.
The invention further provides disengagement of the flight control system if an extreme nonstable event is detected by the disengagement system. In that event, the flight control system is switched to neutral mode for as long as required till the stabilizing system recovers the platform to a state of acceptable stability. After recovering, the flight control system is automatically reengaged.
The invention further provides a higher level of operational safety by due to the invention's architecture of two separate systems. In case of a temporary or major failure in the flight control system, one of its components, or sensors such as GPS (global positioning system), the stabilization system will maintain the platform balanced until recovery or will perform an emergency autorotation landing.
The invention further provides the user with a remote control interface to the flight control system, enabling the user to put the platform into semi-auto mode. In semi-auto mode the flight control system receives its flight parameters in real-time from user commands instead of from the preprogrammed flight plan. In this mode even an unskilled user can pilot the craft by remote control commands. The remote control interface can be software or hardware, for example, commands sent via keyboard.
The general problem solved by this invention is to provide fully autonomous control capability for nonstabilized flight platforms, especially but not limited to small scale platforms, such as short-range model helicopters.
The technology of the present invention enables pre-programmed controlled flight via flight/navigation plan in fully automatic mode. Or the platform can fly in semi-automatic mode, with a novice operator controlling some or all flight parameters using a simple command set. The novice user can, if he wishes, control direction then reengage the autonomous flight control for fully autonomous performance of operations that require pilot skills, such as: takeoff, hovering, flying and landing even in extreme weather conditions, without a need for manned involvement or interference.
The core technology and innovation is based on having separate, but integrated, dynamic stabilization system and flight control system, as well as on a unique output method developed for this application. The closest known technologies offer mainly two separate capabilities, stabilizers and autopilot:                Stabilizers for stabilized or nonstabilized flight platforms        Autopilots for stabilized platforms with some build-in stabilization capabilities        